With any security device you have to ask what are you trying to achieve and which device, or devices can achieve that. You also need to assess what inconvenience you are prepared to tolerate. You also need to keep in mind that nothing is 100% secure.

what are you trying to do?

e.g. Don't want the bike to be removed from where you left. Noisy alarm and physical devices such as chains ground anchors etc.

e.g. Want to make the bike less attractive/worth less to the crims. Security marking like smart water, alpha dot, data tag etc.

Some mates hate alarms and the like that much they just pay up the increased insurance premium.